Sensor powering and low power read out electronics in RFID

Radio frequency identification has rapidly spread throughout the industry as a means to identify and track goods. In many cases, there's a need for measuring and logging of a physical quantity, e.g. temperature of a frozen food in the cold chain. However, as there's very limited power available for the RFID transponder, the integration of sensors is not a trivial task. In this presentation, the sensor powering and readout in RFID is discussed, especially in the case of passive and semipassive UHF RFID. First the the power transfer form the reader and backsacttering modulation are considered, as well as the power available for sensor readout. The fundamental trade-off between captured and scattered power is investigated. Second, different sensor readout electronics and strategies are compared to minimize power consumption. Third, examples of RFID sensor implementations are presented. The talk aspires to give a comprehensive glance at present UHF RFID sensors, and to illustrate the situations, where RFID sensors can and should be used.